1. Field of the Invention
The present invention relates to a silicon-containing polymer and a process for its production. In particular, the invention relates to a silicon-containing polymer that is useful as a primary agent in a resist material composition that provides intricate resist patterns by exposure to radiation with ArF excimer laser light, an electron beam or the like followed by development with an alkali developing solution, and to a process for its production. The invention further relates to a resist composition containing such a polymer, to a method of forming resist patterns using it, and to a method of fabricating electronic devices including LSIs, magnetic heads, liquid crystal devices, MCMs, etc. and photomasks using the method.
2. Description of the Related Art
With the trend toward higher integration and higher functionality of electronic devices, such as semiconductor devices, in recent years, progress continues to be made toward more intricate and multilayered wirings. In the manufacture of second generation semiconductor devices with ever higher integration and higher functionality, research has begun on using ArF excimer lasers and EUV light as exposure light sources in lithography techniques for intricate working, and progress is being made toward shorter wavelength applications. Problems raised with shorter wavelength light sources include the transmittance of the resist materials and reflection from the substrates, but surface imaging has been proposed as an effective technique to counter these problems, and a particularly effective method is the bi-layer resist method employing silicon-containing polymers as resist materials.
According to the bi-layer resist method, an organic resin is coated to a film thickness of 1 μm, for example, to form a lower resist layer on which there is formed an upper resist layer of a thin film of about 0.1-0.2 μm, and then the upper resist layer is first patterned by light exposure and development of the upper layer and the resulting upper layer pattern is used as a mask for etching of the lower layer, to form a resist pattern with a high aspect ratio. The bi-layer resist method can alleviate or prevent the influence of level differences in the substrate and reflection from the substrate surface by the lower layer resist, while the small film thickness of the upper layer resist allows improved resolution compared to single-layer resist methods. Consequently, the bi-layer resist method is more advantageous than the single-layer resist method for formation of intricate patterns on substrates with large level differences and it is therefore believed to be a more effective resist process for the shorter wavelengths of exposure light sources which will be used in the future.
Bi-layer resist materials employing various silicon-containing polymers have been reported to date (for example, Japanese Unexamined Patent Publications SHO No. 58-96654, No. 61-108628, No. 62-104032 and No. 62-220949, Japanese Unexamined Patent Publications HEI No. 1-56732, No. 1-222254, No. 3-29311, No. 5-58446, No. 5-181280, No. 6-95385, No. 6-184311, No. 6-202338 and No. 11-130860), but none of those available have been excellent for alkali development in terms of shelf-life, sensitivity, resolution, O2-RIE resistance, heat resistance, or shorter wavelengths of exposure light sources for pattern intricacy. In particular, none have exhibited excellent developing properties in a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution, which is currently a commonly used alkali developing solution for mass production of LSIs, and this has been a drawback against their application to general purpose developing equipment.